Hi again,
This morning I called Acer again, for the last time I hope, and after explaining the problem again and again, I said that I was going to take the unit back for replacement. They gave me a reference number and off I went to the retailer.
Officeworks just looked at the receipt, the number given by Acer and brought another brand new unit.
i took it home, unpacked, connected the USB cable and voilá! All drivers installed the first time excepting the Android drivers that I installed manually from the Device Manager using the drivers that I downloaded from Acer and they are correct after all. Windows could not find them anywhere.
This time Windows even detected the USB Composite Device and installed the driver correctly. A new entry in Device Manager appeared: Android Tablet/Android Composite ADB Interface.
Yes, the ADB wasn't appearing before and now it is.
Browsing the files, I could see every single folder from the external SD card, more than 500 folders, no problems, the first time.
I believe my problem has been solved replacing the unit but I will not play the trumpets just yet. I am through the process of putting everything that I had back in the unit. I had done an app backup making things easier. Updates are a pain. Will keep you posted if anything changes.
Definitely, the old unit has an issue with the USB related circuitry. Their problem now...
Cheers!
United States